Merge tag 'edac_for_4.5' of git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp

[cascardo/linux.git] / kernel / panic.c

diff --git a/kernel/panic.c b/kernel/panic.c
index 4b150bc..b333380 100644 (file)
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -61,6 +61,17 @@ void __weak panic_smp_self_stop(void)
                cpu_relax();
 }
 
+/*
+ * Stop ourselves in NMI context if another CPU has already panicked. Arch code
+ * may override this to prepare for crash dumping, e.g. save regs info.
+ */
+void __weak nmi_panic_self_stop(struct pt_regs *regs)
+{
+       panic_smp_self_stop();
+}
+
+atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
+
 /**
  *     panic - halt the system
  *     @fmt: The text string to print
@@ -71,17 +82,17 @@ void __weak panic_smp_self_stop(void)
  */
 void panic(const char *fmt, ...)
 {
-       static DEFINE_SPINLOCK(panic_lock);
        static char buf[1024];
        va_list args;
        long i, i_next = 0;
        int state = 0;
+       int old_cpu, this_cpu;
 
        /*
         * Disable local interrupts. This will prevent panic_smp_self_stop
         * from deadlocking the first cpu that invokes the panic, since
         * there is nothing to prevent an interrupt handler (that runs
-        * after the panic_lock is acquired) from invoking panic again.
+        * after setting panic_cpu) from invoking panic() again.
         */
        local_irq_disable();
 
@@ -94,8 +105,16 @@ void panic(const char *fmt, ...)
         * multiple parallel invocations of panic, all other CPUs either
         * stop themself or will wait until they are stopped by the 1st CPU
         * with smp_send_stop().
+        *
+        * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which
+        * comes here, so go ahead.
+        * `old_cpu == this_cpu' means we came from nmi_panic() which sets
+        * panic_cpu to this CPU.  In this case, this is also the 1st CPU.
         */
-       if (!spin_trylock(&panic_lock))
+       this_cpu = raw_smp_processor_id();
+       old_cpu  = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
+
+       if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)
                panic_smp_self_stop();
 
        console_verbose();
@@ -117,9 +136,11 @@ void panic(const char *fmt, ...)
         * everything else.
         * If we want to run this after calling panic_notifiers, pass
         * the "crash_kexec_post_notifiers" option to the kernel.
+        *
+        * Bypass the panic_cpu check and call __crash_kexec directly.
         */
        if (!crash_kexec_post_notifiers)
-               crash_kexec(NULL);
+               __crash_kexec(NULL);
 
        /*
         * Note smp_send_stop is the usual smp shutdown function, which
@@ -142,9 +163,11 @@ void panic(const char *fmt, ...)
         * panic_notifiers and dumping kmsg before kdump.
         * Note: since some panic_notifiers can make crashed kernel
         * more unstable, it can increase risks of the kdump failure too.
+        *
+        * Bypass the panic_cpu check and call __crash_kexec directly.
         */
        if (crash_kexec_post_notifiers)
-               crash_kexec(NULL);
+               __crash_kexec(NULL);
 
        bust_spinlocks(0);